The present invention relates to fuel injection quantity control apparatus and method for a diesel engine, and in particular to a method and apparatus for optimally controlling the fuel injection quantity into cylinders of the diesel engine in accordance with engine operating conditions.
A system for controlling fuel injection quantity into cylinders of a diesel engine of a motor vehicle is known in which an electronically controlled injection system incorporated with a distribution type fuel injection pump wherein fuel is injected into the cylinders in accordance with the operation of a fuel injection valve such as solenoid-operated valve.
One example of such prior art system for controlling fuel injection quantity is disclosed in Japanese Patent Provisional publication No. 58-187537, in which the timing of the solenoid-operated valve, i.e., fuel spilling timing is controlled in accordance with engine rotational speed at the time. More specifically, the timing control is effected so as to energize the solenoid-operated spill valve upon elapse of a predetermined time period after the detection of a reference signal produced each time the engine crank shaft rotates by a predetermined angle, the predetermined time period being measured by operating a timer counter provided in a microcomputer in response to the generation of the reference signal.
Such prior art system would suffer no problem as long as the engine rotation is smooth and has no variations. However, the engine is actually subjected to rotational variations or irregularities in its one cycle of the operation and rapid variations of engine rotational speed. These variations cause the occurrence of injection timing errors, thus resulting in worsening the fuel injection quantity control from the viewpoint of accuracy.